This is an on-going project examining the utility of the cocaine discrimination procedure as a human laboratory model of cocaine abuse liability. First we evaluated whether an oral dose of cocaine can serve as a discriminative stimulus in humans. Five volunteers were studied. We then examined whether the discriminative stimulus effects of two CNS stimulants with differing pharmacological mechanisms of action are similar to those of cocaine. Two cocaine-abusing volunteers have completed the entire protocol. We plan to begin examining whether the dopamine agonist haloperidol alters the discriminative stimulus effects of cocaine in humans trained to discriminate cocaine from placebo.